They're generally gentler, but it kind of depends on the highway. The speeds also mean more consequences of any pothole or other obstruction, too.

But mostly the observation is that you'll likely get a lot more miles on the car in such a rental than a local rental. So a rental company that keeps a car in their fleet for 2-years or 20,000 miles is going to likely send most EVs out for age and more ICEs for milage (in my estimation, anyway), and so sure, ICEs will have oil changes in that interval, but they'll also have more of the every car needs maintenance sort of proportional to use (runtime and/or mileage), because they'll see more use.